The present invention relates to a fixation device for releasably fastening an object provided with a through-hole, and more specifically to a fixation device for fastening a spare wheel to a vehicle.
It is known from, for example, U.S. Pat. No. 4 423 900 to use a fixation device which comprises three distinct parts, namely a screw part, a nut part and an attachment part for fixing a spare wheel to a vehicle. The screw part is screwed into the attachment part and, in order to release the spare wheel, either the screw part or the nut part must be turned through a number of revolutions so that the screw part or the nut part is screwed from its threaded engagement with its respective part. On the other hand, it is necessary that the screw part or the nut part must be threaded into the attachment part or onto the screw part respectively. This requires great accuracy and is often problematic in poor light conditions, leading to the risk of damaging the screw threads and therefore consequent mounting problems. The threaded connection between the screw part and the attachment part certainly gives a very tight connection, but can lead to the risk of deformation of the screw part, again with consequent mounting problems. Alternatively, the base of the screw part can be welded to the attachment part or directly to the vehicle. Here, though, there exists the risk of fissures developing at the attachment location resulting from the transverse forces which arise from the unavoidable movement of the spare wheel.
Another type of spare wheel mounting is described in JP 58-81869. Instead of having a threaded attachment part as in the above-mentioned US document, the attachment part of the JP arrangement is provided with a slot into which protrusions on a corresponding screw part fit. The attachment part is mounted behind the surface to which the spare-wheel is to be fastened and so a similar slot is also required in this surface. A nut part is provided on the end of the screw part remote from said protrusions and acts on a forcible connector to tighten said connector to the spare wheel. This slot and protrusion arrangement overcomes the necessity of trying to thread the attachment, screw and nut parts together. However, such an arrangement is prohibitively expensive due not only to the number of parts required, but also to the need to provide a slot in the fastening surface. Since a slot has to be provided, the risk of corrosion is introduced.
The object of the present invention is to eliminate the above-mentioned problems and to provide a fixation device which, in a quick and safe way, permits a releasable fixation of an object.